The invention relates to a control process for pump device comprising a pump equipped with a flexible tube.
In current medical practice, drop-by-drop infusion devices are used to administer solutions to patients at a relatively slow rate. These drop-by-drop devices comprise a tube connecting the container with the solution to the patient and a volumetric pump controlling the rate of flow. To ensure the patient""s safety, it is essential that the flow of solution be controlled as it passes through the drop-by-drop device. To accomplish this, it is common to add to the pump a drop detector, generally comprising an optical detector connected to the drip chamber of the drop-by-drop device.
These detectors provide a high degree of safety and are able to detect underflow situations during which no drops are formed due, for example, to blockage of the tube, improper tube positioning in the pump, or reversal of the direction of the tube in the pump. The detectors also detect overflow situations during which drops flow too rapidly (the normal rate being approximately 20 drops per minute) or so rapidly that they form a continuous stream of solution, for example, as a result of tube rupture, poor tube positioning in the pump, or a pump defect.
Such drop detectors are highly sensitive and can trigger false alarms. Sometimes false data can be generated if the drip chamber is tilted or if drops are present on the wall of the drip chamber.
The present invention provides a control process for a pump device comprising a pump equipped with a flexible tube similar to those used for drop-by-drop infusion, that avoids the drawbacks of the known process and that uses a drop detector.
In one aspect, the invention is a control process for a pumping device that comprises a pump equipped with a flexible tube, the process comprising the steps of blocking said flexible tube by means of an occlusion device located downstream of said pump, starting said pump, and measuring an instantaneous pressure in a section of said flexible tube situated between said pump and said occlusion device. The process also includes adjusting said pump for a flow rate substantially equal to a maximum flow, performing a predetermined number of cycles, said number of cycles being at least equal to 1, stopping the pump, and triggering an alarm if the instantaneous pressure does not reach a threshold pressure value after the predetermined number of cycles.
In another aspect, the invention is a control device for a pumping device with a pump, comprising a flexible tube introduced into the pump, an occlusion device located downstream of said pump, and a pressure detector located between said pump and said occlusion device for measuring an instantaneous pressure.
In the process consistent with the invention, the flexible tube is obstructed by means of an occlusion device located downstream of the pump. The pump is started, and the instantaneous pressure Pi is measured in the section of the tube located between the pump and the occlusion device. Before beginning the infusion, the infusion tube is blocked downstream of the pump and the pump is allowed to operate against this obstacle. Over pressure must be developed in the section of the tube located between the pump and the occlusion whose instantaneous value is measured.
If the pump is defective, during the pumping process a moment will occur during which there is no occlusion zone. In this case the over pressure will decrease, because of a reflux of liquid during the period in which the occlusion zone reappears. This loss of pressure can be detected by measuring the instantaneous pressure Pi.
When the pump is used for infusion, such defects can occur over a period of time during which the flow of solution will be uncontrolled, and such a situation repeats at regular intervals. Similarly, no over pressure will occur if the tube occlusion is located upstream of the pump, if the tube is poorly positioned in the pump, or if the direction of the tube in the pump is reversed.
According to the invention, the following steps are carried out:
a) the pump after being adjusted for a low rate close to the maximum flow rate, performs a number of predetermined cycles at least equal to one, after which it is stopped; and
b) an alarm is triggered if the instantaneous pressure Pi, measured throughout step a, does not reach a threshold value P1 by the end of step a.
To provide sufficient control, it is essential that the complete pumping cycle be monitored. For reasons of safety it is preferable that this take place for slightly more than one cycle, for example 1.1 cycles. If the pump is defective, the increased pressure will not be constant and the pump will fail to reach the threshold value at the end of the programmed rotation. The threshold value is calculated statistically for the individual pump type.
Another aspect of the invention involves carrying out the following additional steps when no alarm is triggered during step b described above. These steps are:
c) after being adjusted to an intermediate flow rate, the pump performs a number of predetermined cycles at least equal to 1 and is then stopped;
d) the minimum pressure, Pmin, and maximum pressure, Pmax, reached during the previous step, are measured; and
e) an alarm is triggered if the minimum pressure Pmin, or maximum pressure Pmax, determined in step d do not reach the threshold values P2 and P3 respectively.
The intermediate flow rate chosen during step c can be used to detect any pressure loss while ensuring a relatively short control period, for example less than about 10 sec.
Another advantageous aspect of the process involves the triggering of an alarm during step 1 if the instantaneous pressure Pi reaches a threshold value P4 during step c. This involves detecting the formation of excessive over pressure capable of damaging the tube or pump.
To restore the infusion device to its normal operating state, an additional step g can be performed during which the pump is operated in the reverse direction for the exact number of cycles carried out during the previous steps. The occlusion device is also reopened at the end of the process if no alarm has been triggered. By taking this precaution, the control process can be accomplished both during an occlusion and at other times. This step is also necessary when the process is automated.
This process according to the invention is particularly well suited for application to finger pumps. However, it can also be used to detect a possible fracture of the pump support bracket.
A device for implementing the control process according to the invention can comprise, for example, a flexible tube, a pump in which the flexible tube is introduced, an occlusion device located downstream of the pump, and a pressure detector located between the pump and the occlusion device.
In a preferred embodiment the device for implementing the process incorporates a second pressure detector located upstream of the pump. This second assure detector can be used to detect an occlusion or rupture of the tube upstream of the pump, during the control process itself and during the infusion.
According to the invention, the device implementing the procedure can incorporate a control unit that can be used to control the opening and closing of the occlusion device; adjust the flow rate and on/off operation of the pump for the number of cycles determined in steps a and c; analyze the measured instantaneous pressure Pi for steps b, d, e, and f; stop the pump whenever an alarm is generated; and run the pump in reverse for the number of cycles identified in the previous steps. The device for implementing the process can preferably operate automatically.
During operation, the control unit closes the tube occlusion device, adjusts the rate of flow of the pump to a value near the maximum, then causes it to operate for 1.1 cycles, for example, while analyzing the values supplied by the pressure detector. During the second stage of the process, the control unit adjusts the rate of flow of the pump to an intermediate value and causes the pump to operate for 1.1 cycles, for example, while analyzing the values for instantaneous pressure Pi supplied by the pressure detector.
This same control unit can trigger alarms in the event these values are out of range. If, however, the control reveals no abnormalities, the unit causes the pump to operate in reverse for the same number of cycles it operated during the previous steps, and reopens the occlusion device. It is possible to program this control unit to perform the control process at the start of each infusion, and also during said infusion.
To increase safety it may be advantageous introduce the tube into e pump only in a predetermined direction. In this case, for example, the tube could include a device shaped like an arrow, indicating the direction of flow of the liquid, similar to the clamp described in French patent application 9901132.